It’s neither a bird nor a plane, but a winged microchip as small as a grain of sand that can be carried by the wind as it monitors such things as pollution levels or the spread of airborne diseases.
The tiny microfliers, whose development by engineers at Northwestern University was detailed in an article published by Nature this week, are being billed as the smallest-ever human-made flying structures.
Mini spy fliers
The devices don’t have a motor; engineers were instead inspired by the maple tree’s free-falling propeller seeds — technically known as samara fruit.
The engineers optimized the aerodynamics of the microfliers so that “as these structures fall through the air, the interaction between the air and those wings cause a rotational motion that creates a very stable, slow-falling velocity,” said John A. Rogers, who led the development of the devices.
“That allows these structures to interact for extended periods with ambient wind that really enhances the dispersal process,” said the Northwestern professor.
The wind would scatter the tiny microchips, which could sense their surrounding environments and collect information. The scientists say they could potentially be used to monitor for contamination, surveil populations or even track diseases.
Their creators foresee microfliers becoming part of “large, distributed collections of miniaturized, wireless electronic devices.” In other words, they could look like a swarm.
The concept has also found its way to the dystopian science fiction series Black Mirror.
What are these microflyers capable of?
The microfliers comprise two parts: millimeter-sized electronic functional components and their wings. As the microflier falls through the air, its wings interact with the air to create a slow, stable rotational motion. The weight of the electronics is distributed low in the center of the microflier to prevent it from losing control and chaotically tumbling to the ground.
In demonstrated examples, Rogers’ team included sensors, a power source that can harvest ambient energy, memory storage and an antenna that can wirelessly transfer data to a smart phone, tablet or computer.
In the lab, Rogers’ group outfitted one device with all of these elements to detect particulates in the air. In another example, they incorporated pH sensors that could be used to monitor water quality and photodetectors to measure sun exposure at different wavelengths.
Rogers imagines that large numbers of devices could be dropped from a plane or building and broadly dispersed to monitor environmental remediation efforts after a chemical spill or to track levels of air pollution at various altitudes.
“Most monitoring technologies involve bulk instrumentation designed to collect data locally at a small number of locations across a spatial area of interest,” Rogers said. “We envision a large multiplicity of miniaturized sensors that can be distributed at a high spatial density over large areas, to form a wireless network.”
And I say, there’s just a small step going from environmental surveillance to human surveillance… What do you think?
They think they can beat nature
But unlike with maple seeds, the engineers needed to slow down the descent of their microfliers to give the devices more time to collect data. Team member Yonggang Huang developed a computer model that calculated the best design that would enable the microfliers to fall slowly and disperse widely.
“This is impossible with trial-and-error experiments,” Huang said in a Northwestern news release.
The team also drew inspiration from children’s pop-up books for the construction of such tiny devices.
The engineers first created a base and then bonded it to “a slightly stretched rubber substrate,” according to the news release. When relaxed, that substrate pops up into a precise three-dimensional shape.
“We think that we beat nature,” Rogers said. “At least in the narrow sense that we have been able to build structures that fall with more stable trajectories and at slower terminal velocities than equivalent seeds that you would see from plants or trees.” [NPR, nature, Northwestern]
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